Effects of Saccharomyces cerevisiae supplementation on apparent total tract digestibility of nutrients and fermentation profile in healthy horses.
Authors: Mackenthun E, Coenen M, Vervuert I
Journal: Journal of animal physiology and animal nutrition
Summary
# Editorial Summary Saccharomyces cerevisiae (baker's yeast) is frequently marketed as a digestive supplement for horses, with the premise that it can enhance fibre digestion by modifying the hindgut microbial population; however, evidence supporting this claim remains limited. Mackenthun and colleagues conducted a crossover trial with twelve geldings fed a standardised diet of cracked corn and hay, testing three treatment groups: control (no supplementation), 1 g SC daily (2 × 10¹⁰ cfu), and 3 g SC daily, with faecal collections analysed for nutrient digestibility, microbial viability, and fermentation markers including short-chain fatty acids, lactic acid, and pH. Crucially, only a marginal fraction of the supplemented yeast survived passage through the digestive tract—faecal recovery was approximately 1.1 × 10⁶ cfu at the 1 g dose and 3.6 × 10⁶ cfu at the 3 g dose—and neither fibre digestibility, nitrogen digestibility, nor fermentation profiles showed any significant treatment-related changes across the supplementation regimes. For practitioners working with intact, healthy horses, these findings suggest that yeast supplementation is unlikely to establish meaningful colonisation in the equine hindgut and therefore cannot be relied upon to enhance forage digestion or modify the fermentation environment, challenging the theoretical basis for its use as a routine digestive aid in this population.
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Practical Takeaways
- •Saccharomyces cerevisiae supplementation does not improve fibre digestibility in healthy horses consuming typical grain and hay diets
- •The low faecal recovery of supplemented yeast suggests it does not establish in the equine gut, limiting its potential probiotic effects
- •This supplement cannot be recommended as a strategy to enhance nutrient digestibility or modify hindgut fermentation in healthy horses
Key Findings
- •Saccharomyces cerevisiae supplementation at 1 or 3 g daily did not significantly affect apparent total tract digestibility of crude fibre (approximately 40% across all groups)
- •Recovery of SC in faeces was marginal: 1.1 × 10^6 cfu from 1 g dose and 3.6 × 10^6 cfu from 3 g dose, both substantially lower than supplemented amounts
- •Short-chain fatty acids, lactic acid, and faecal pH were not significantly affected by SC supplementation
- •SC colonization and proliferation in the healthy equine intestinal tract appears unlikely based on low recovery rates and unchanged fermentation profiles